Rapid test for the serological separation of staphylococci from micrococci

Comparison of methods for routine separation of coagulase-negative staphylococci from micrococci isolated from sheep

A total of 176 Gram-positive, catalase positive cocci strains, isolated from sheep were studied by different routine tests for the differentiation of staphylococci and micrococci, comparing their validity and usefulness. By glucose fermentation and growth in the anaerobic portion of thioglycolate 85 and 73.6% respectively of coagulase negative staphylococci were misclassified as Micrococcus spp. Susceptibility to lysostaphin was an adequate test for the differentiation of the strains. Atypical results in the production of acid from glycerol/erythromycin were obtained in 11.8% of the coagulase negative strains and 16.7% of micrococci. The combined use of the selective media furazolidone agar and Schleifer and Krämer medium resulted in a fast and useful separation of ovine staphylococci and micrococci. The bacteriolytic activity misclassified 32.2% of the coagulase negative strains.

Immunoelectron microscopic studies on the localization of peptidoglycan peptide subunit pentapeptides in bacterial cell walls

The peptide subunit pentapeptide H-L-Ala-D-Glu(L-Lys-D-Ala-D-Ala-OH)-NH2 of peptidoglycan was localized in the cell walls of several Gram-positive bacteria employing the indirect immunoferritin technique. Specific antibodies to the D-alanyl-D-alanine moiety of non-crosslinked peptide subunit pentapeptide were raised in rabbits by immunization with synthetic immunogen albumin-(CH2CO-Gly-L-Ala-L-Ala-D-Ala-D-Ala-OH)39. Specificity of these antibodies for the peptide subunit pentapeptide and not for the peptide subunit tetrapeptide was corroborated in a Farr-type radio-active hapten binding assay. Specificity of labelling with ferritin was established by immunoelectron microscopic controls, and by the excellent correlation between specific labelling of cells with ferritin and the particular peptidoglycan primary structure of bacterial strains investigated. Cells of Lactobacillus gasseri, Streptococcus pyogenes and Staphylococcus aureus revealing non-crosslinked peptide subunit pentapeptides in their peptidoglycans could specifically be labelled. Lactobacillus acidophilus and Bacillus subtilis, on the contrary, missing such pentapeptides, failed in labelling. The implication of this method to possibly localize the points of attack of penicillin or cycloserine is discussed.

Comparison of various methods for differentiation of staphylococci and micrococci

A modified oxidase test (Remel, Lenexa, Kans.) and susceptibility to furazolidone and lysostaphin (Remel) were evaluated in conjunction with the Staph-Ident strip (Analytab Products, Plainview, N.Y.) to accurately differentiate between staphylococci and micrococci. A total of 414 clinical isolates of catalase-positive, gram-positive cocci were each tested with the Staph-Ident strip and by glucose fermentation, acid production from glycerol, susceptibility to furazolidone and lysostaphin, and the oxidase test. Based on the reference methods of glucose fermentation and acid production from glycerol, 396 (95.6%) of the organisms were classified as Staphylococcus species and 18 (4.4%) were classified as Micrococcus species. Of the staphylococci, 99% were oxidase negative and susceptible to furazolidone; 82% were susceptible to lysostaphin. All of the micrococci were oxidase-positive and resistant to furazolidone and lysostaphin. Of the staphylococci, 99% were identified to species by the Staph-Ident strip. However, six (33%) of the micrococci were incorrectly identified as Staphylococcus species (three each of Staphylococcus hominis and Staphylococcus saprophyticus). Because of the demonstrated sensitivity and specificity of the oxidase and furazolidone susceptibility tests, it is suggested that either of these methods be used in the clinical laboratory to accurately differentiate between staphylococci and micrococci. It is also suggested that when working with the Staph-Ident strip, additional testing such as furazolidone susceptibility or oxidase activity should be performed to provide increased accuracy in the differentiation and characterization of members of the family Micrococcaceae.

Modified oxidase and benzidine tests for separation of staphylococci from micrococci

Two simple and rapid methods for the separation of staphylococci from micrococci are described. They are based on modified oxidase and benzidine tests. Micrococci and Staphylococcus sciuri yield a blue color with a 6% solution of tetramethylphenylenediamine in dimethyl sulfoxide, whereas all of the other staphylococci exhibit no coloration. Best's results were obtained with overnight cultures on blood agar. The presence of c-type cytochromes i micrococci and S. sciuri could be detected with benzidine; all noncovalently linked heme groups are removed before the addition of the benzidine reagent. The oxidase test is the simplest and most rapid method for the separation of staphylococci (except S. sciuri) from micrococci, if the nutritional requirements and the time of incubation are strictly followed. This test is especially recommended for the examination of clinical material in which S. sciuri is usually not found.

Rapid distinction between micrococci and staphylococci with furazolidone agars

Furazolidone agar proved to be a suitable medium for separating strains of the genera Micrococcus and Staphylococcus. 720 isolates (including 24 type strains) of gram- and catalase-positive cocci were tested for growth on tryptone soya and peptone agar with the addition of 50 microgram/ml furazolidone. The results were compared with the classification obtained by the standard-O/F-test and by the test system of Schleifer and Kloos. For routine identification and separation of staphylococci from micrococci a peptone agar with 20 microgram furazolidone/ml is recommended.